KR102261450B1 - screw extruder - Google Patents

Abstract

Provided is a screw extruder having a configuration capable of increasing the dispersion and mixing properties of materials. The screw-type extruder 1 is equipped with screws 2 and 3, and the casing 4 which accommodates the screws 2 and 3 and in which the inlet 11 of the material was provided in the upstream. With respect to the clearance between the top part 12 of the flight part 7 and the inner wall surface of the casing 4, the clearance C2 in the downstream end of the flight part 7 of the screws 2 and 3 is It is larger than the clearance C1 in the downstream end part 11a of (11), and between the downstream end part 11a of the inlet 11 and the downstream end part of the flight part 7 WHEREIN: Upstream There is no area in which the clearance is reduced from the side toward the downstream side.

Description

screw extruder

The present invention relates to a screw extruder for extruding a kneaded material, and particularly relates to a screw extruder suitably used to form a sheet shape while extruding a kneaded material.

In the manufacturing process of a tire for automobiles, an extrusion molding machine is used that is installed under a kneader of rubber, which is a raw material of a tire, and forms a sheet shape while continuously extruding rubber (kneaded product) input from the kneader. As a technique regarding this kind of extrusion molding machine, there exists a thing described in the following patent document 1, for example.

The sheet forming apparatus described in Patent Document 1 includes a material supply unit for extruding and supplying a material, a material storage unit for temporarily storing the material extruded and supplied, a material pressing unit for applying a pressing force to the stored material, and It is provided with a material rolling part which shape|molds the existing material into a sheet form and dispenses it, and the control part which controls operation. The said material supply part is equipped with the twin-shaft taper screw, The biaxial taper screw is accommodated in the casing.

According to FIG. 7 etc. of patent document 1, the clearance (gap dimension) between the top of the spiral flight part of the said tapered screw and the inner wall surface of a casing is constant from an upstream side to a downstream side.

Japanese Patent Laid-Open No. 2011-73428

In recent years, the demand for fuel-efficient tires is increasing. Silica is often blended in a high proportion of rubber, which is a raw material for fuel-efficient tires. A rubber (kneaded product) containing silica in a high proportion has a problem in that it is difficult to mold into a sheet shape in an extruder. Therefore, it is desired to improve the dispersion and miscibility of the rubber (kneaded product) not only in the kneader of the upstream process but also in the extrusion molding machine.

However, in the sheet forming apparatus described in Patent Document 1, as described above, the clearance (gap size) between the top of the spiral flight portion of the tapered screw and the inner wall surface of the casing is constant from the upstream side to the downstream side, In the material supply section, the material is not particularly kneaded. That is, in the sheet forming apparatus of patent document 1, the dispersion-mixability of a material cannot be improved.

This invention was made in view of the said situation, and the objective is to provide the screw type extruder of the structure which can improve the dispersion-mixing property of a material.

The screw-type extruder which concerns on this invention is a screw-type extruder which extrudes the kneaded material provided with the casing which accommodates a screw and the said screw, and the inlet of the material was provided in the upstream. The said screw has a shaft part and the spiral flight part provided in the outer peripheral surface of the said shaft part. With respect to the clearance between the top portion of the flight portion and the inner wall surface of the casing, the clearance at the downstream end of the flight portion is greater than the clearance at the downstream end of the inlet, and Between the downstream end and the downstream end of the flight part, there is no region in which the clearance is reduced from the upstream side to the downstream side.

According to this structure, in the downstream between the downstream edge part of the inlet port of a material, and the downstream edge part of the flight part of a screw, not only conveying material but kneading|mixing is possible. That is, according to the screw extruder which concerns on this invention, the dispersion-mixing property of a material can be improved.

In the present invention, it is preferable that there is a region in which the clearance is constant in at least any one of an upstream portion and a downstream portion between the downstream end of the inlet and the downstream end of the flight portion.

The said upstream part is a part in which the conveyance function of a material is exhibited, and the said downstream part is a part in which the kneading|mixing function of kneading a material is exhibited. According to this structure, the conveyance function and/or the kneading|mixing function of a material can be stabilized. Further, between the downstream end of the material inlet and the downstream end of the flight portion of the screw, it is easier to manufacture the flight portion of the screw or the casing than when the clearance is continuously changed over the entire length.

Further, in the present invention, it is preferable that there is a region in which the clearance is constant in each of the upstream portion and the downstream portion between the downstream end of the inlet and the downstream end of the flight portion.

According to this configuration, both the material feeding function and the kneading function can be stabilized. Moreover, manufacture of the flight part of a screw, or manufacture of a casing is easier.

Further, in the present invention, between the downstream end of the inlet and the downstream end of the flight portion, there is a clearance step portion in which the clearance expands stepwise from the upstream side to the downstream side, and the upstream side of the clearance step portion And it is preferable that the said clearance on the downstream side is made constant in each.

According to this structure, manufacture of the flight part of a screw or manufacture of a casing is easier than the case where the clearance changes continuously.

Further, in the present invention, between the downstream end of the inlet and the downstream end of the flight portion, there is a clearance expanding portion in which the clearance is linearly expanded from the upstream side to the downstream side, and the upstream side of the clearance expanding portion and It is preferable that the said clearance on the downstream side becomes constant in each.

According to this configuration, it is possible to prevent retention of the material at the position where the clearance is changed.

Further, in the present invention, in the axial direction of the shaft portion, the distance between the downstream end of the flight portion and the downstream end of the inlet is L, and the distance between the downstream end of the flight portion and the clearance step portion is Lm. In this case, it is preferable that 0.25 < Lm/L.

According to this configuration, the amount of material passing through the clearance portion is increased, and uniform kneading of the material can be promoted.

In the present invention, it is preferable that 0.25<Lm/L≤0.4.

According to this configuration, the amount of the material passing through the clearance portion can be increased while maintaining the pressure-increasing capacity (feeding capacity) high, and uniform kneading of the material can be promoted.

Further, in the present invention, in the axial direction of the shaft portion, the distance between the downstream end of the flight portion and the downstream end of the inlet is L, between the downstream end of the flight portion and the axial center position of the clearance expanding portion When the distance of is Lm, it is preferable that 0.25<Lm/L.

According to this configuration, the amount of material passing through the clearance portion is increased, and uniform kneading of the material can be promoted.

In the present invention, it is preferable that 0.25<Lm/L≤0.4.

According to this configuration, the amount of the material passing through the clearance portion can be increased while maintaining the pressure-increasing capacity (feeding capacity) high, and uniform kneading of the material can be promoted.

Moreover, in this invention, it is preferable that the said clearance changes according to the outer diameter of the top of the said flight part.

According to this configuration, it is possible to prevent retention of material in the clearance change portion rather than the case where the clearance is changed according to the shape and size of the casing. In addition, according to the outer diameter of the top of a flight part, manufacture of the screw type extruder is easy when the clearance is changed.

Further, in the present invention, there is provided a pressure sensor for measuring the pressure inside the casing in a region where the clearance on the downstream side between the downstream end of the inlet and the downstream end of the flight portion is constant, It is preferable that the rotation speed of the said screw is controlled according to the pressure measured by this.

According to this structure, kneading|mixing of a material can be controlled easily.

According to the screw-type extruder which concerns on this invention, the dispersion-mixability of the supplied material can be improved in the said screw-type extruder.

BRIEF DESCRIPTION OF THE DRAWINGS It is a top sectional view of the extruder provided with the roller die as one Embodiment of the screw type extruder which concerns on this invention.
Fig. 2 is a cross-sectional view taken along line AA of Fig. 1, and is a longitudinal cross-sectional view of an extruder provided with a roller die according to an embodiment of the present invention.
It is a figure which shows typically the change of the screw axial direction of the clearance between the top of a flight part and the inner wall surface of a casing of the extruder provided with the roller die shown in FIG. 1, FIG.
4 is a flow analysis showing the relationship between the mixing part ratio (ratio of large and small clearance) of the flight part and the amount of material leaking in the reverse direction from the clearance part in the extruder equipped with the roller die shown in FIGS. 1 and 2 in flow analysis. It is a graph showing the results of investigation by
Fig. 5 is a graph showing the results of investigation of the relationship between the mixing portion ratio (ratio of large and small clearance) of the flight portion and the pressure raising ability by flow analysis in the extruder provided with the roller die shown in Figs. 1 and 2 .
Fig. 6 is a view corresponding to Fig. 3, showing a second embodiment of the clearance between the top of the flight portion and the inner wall surface of the casing;
Fig. 7 is a view corresponding to Fig. 3, showing a first modification of the clearance between the top of the flight portion and the inner wall surface of the casing;
Fig. 8 is a view corresponding to Fig. 3, showing a second modification of the clearance between the top of the flight portion and the inner wall surface of the casing;
Fig. 9 is a view corresponding to Fig. 3, showing a third modification of the clearance between the top of the flight portion and the inner wall surface of the casing;

EMBODIMENT OF THE INVENTION Hereinafter, it demonstrates, referring drawings for the form for implementing this invention. The screw extruder shown in the following embodiment is a screw extruder provided with a roller die which extrudes and molds the kneaded material of polymeric materials, such as rubber|gum, into a sheet form (hereinafter referred to as "an extruder with a roller die"). Further, the screw extruder of the present invention can also be used for a machine called a pelletizer that extrudes a kneaded material of a polymer material from a die having a large number of circular holes and then cuts and molds it into cylindrical pellets.

(First embodiment)

The extruder 1 provided with the roller die which concerns on one Embodiment of this invention is demonstrated, referring FIGS. The extruder 1 provided with the roller die has a total of two right and left pairs of screws 2 and 3 which extrude a kneaded material, and the casing 4 which accommodates the screws 2 and 3. A total of two rollers 8 and 9 of a pair of upper and lower are arranged in front of the casing 4 . A portion between the casing 4 and the rollers 8 and 9 is called a bank portion 10 , and the kneaded material extruded by the screws 2 and 3 is stored in the bank portion 10 . The rollers 8 and 9 are connected so as to rotate in opposite directions to each other, and are rotated at the same number of revolutions by one driving means (not shown). The rollers 8 and 9 are for rolling the kneaded material and shape|molding it into a sheet form (sheet 50), and it is called a roller die.

The screws 2 and 3 each have a shaft portion 6 and a helical flight portion 7 provided on the outer peripheral surface of the shaft portion 6 . The screw 2 and the screw 3 are screws of the same shape and size except that the twist angle of the flight is opposite to each other. In addition, the screws 2 and 3 are connected so as to rotate in the opposite direction to each other, and are rotated at the same number of revolutions by one driving means not shown.

The casing 4 has a shape tapering toward the end, and has a casing upstream portion 13 having an inlet 11 for a material (kneaded product) provided at the top thereof, and a casing downstream portion 14 surrounded by a wall surface. The kneaded material, such as rubber, supplied to the inlet 11 from above is extruded to the bank part 10 by the screws 2 and 3 mutually rotating in opposite directions, and thereafter, between the rollers 8 and 9 It is molded into a sheet shape by passing through.

As shown in FIG. 2 , a pressure sensor 5 is provided at the bottom of the casing downstream portion 14 surrounded by a wall surface. The pressure (pressure of the kneaded material) inside the casing downstream portion 14 is measured by the pressure sensor 5 . Moreover, the pressure sensor 5 is provided so that the front-end|tip part (pressure detection part) may not protrude from the inner wall surface of the casing 4 so that it may not contact the flight part 7 of the rotating screws 2 and 3 .

Here, in the present invention, in the extruder 1 itself equipped with a roller die, in order to increase the dispersion and mixing of materials, the clearance (gap) between the top part 12 of the flight part 7 and the inner wall surface of the casing 4 ), the clearance C2 in the downstream end of the flight part 7 is made larger than the clearance C1 in the downstream end 11a of the inlet 11, and the downstream end of the inlet 11 is Between (11a) and the downstream end of the flight portion 7, there is no region in which the clearance is reduced from the upstream side to the downstream side.

Thereby, on the downstream side between the downstream end 11a of the material inlet 11 and the downstream end of the flight part 7 of the screws 2 and 3, the material is transferred (pressurized). ) as well as kneading.

In the embodiment shown in Figs. 1 to 3, between the downstream end portion 11a of the inlet 11 and the downstream end portion of the flight portion 7, the clearance expands stepwise from the upstream side toward the downstream side. A clearance step 21 is provided (refer to Fig. 3). Then, with the clearance step 21 as a boundary, the upstream clearance of the clearance step 21 is constant at C1, and the clearance on the downstream side of the clearance step 21 is constant at C2 (C2>C1). is to be done

In addition, the flight part 7 is helical as mentioned above. Therefore, the clearance between the top part 12 of the flight part 7 and the inner wall surface of the casing 4 also becomes spiral. 3 : is a figure which shows typically the change of the screw axial direction of this clearance, and does not show the form of clearance when the screws 2 and 3 and the casing 4 are seen in cross section (FIGS. 6-9). the same for ). The clearance form at the time of seeing the screws 2 and 3 and the casing 4 in cross section becomes like FIG. 1, FIG.

In this embodiment, the said clearance is changed by changing the outer diameter of the top part 12 of the flight part 7 . The inner wall surface of the casing 4 opposite to the top 12 of the flight portion 7 is a straight line when viewed in its cross section. In the clearance step portion 21, the outer diameter of the top portion 12 of the flight portion 7 is changed stepwise by the difference between the clearance C2 and the clearance C1.

By changing the outer diameter of the top part 12 of the flight part 7, by changing the clearance between the top part 12 and the inner wall surface of the casing 4, the clearance is changed according to the shape and size of the casing 4 Production of the extruder becomes easier than the case. Moreover, retention of material in the clearance change part can also be prevented.

In addition, the pressure sensor 5 described above is located inside the casing 4 in a region where the downstream clearance between the downstream end 11a of the inlet 11 and the downstream end of the flight part 7 is C2. The extruder 1 provided with a roller die is controlled so that the rotation speed of the screws 2 and 3 is controlled according to the pressure (pressure of the kneaded material) measured by the pressure sensor 5, and the extruder 1 with a roller die is controlled. . For example, if the pressure measured by the pressure sensor 5 is lower than the predetermined pressure Pmin, the rotation speed of the screws 2 and 3 increases, and if it is higher than the predetermined pressure Pmax, the screw ( The number of revolutions of 2 and 3) is reduced. When a pressure is between Pmax and Pmin, the rotation speed of the screws 2 and 3 at that time is maintained as it is. By measuring the pressure on the downstream side inside the casing 4 in a region where the clearance is C2 (C2 > C1), and controlling the rotation speed of the screws 2 and 3 according to the measured pressure, the kneading of the material can be easily controlled. can

L, the distance between the downstream end portion of the flight portion 7 and the downstream end portion 11a of the inlet 11 in the axial direction of the screws 2 and 3 (shaft portion 6) is L, and the flight portion 7 When the distance between the downstream end of ) and the clearance step part 21 is Lm, if Lm/L is increased, the area with a large clearance is widened, and in this part, in the direction opposite to the extrusion direction of the material, the material The amount of leakage is increased. If the amount of material leaking in the direction opposite to the direction of extrusion of the material is increased, distributive mixing of the material is promoted. That is, the region where the clearance is C2 (the region of the length Lm in the axial direction) is a region where material mixing (distributive mixing) is promoted. On the other hand, when the amount of material leaking in the direction opposite to the extrusion direction of the material is increased, the pressure-increasing ability of the material is lowered. In addition, the area|region where the clearance is C1 (C1<C2) is the area|region where extrusion (pressure raising) of a material is made|formed.

The present inventors investigated the relationship between Lm/L and the amount of leakage of the material, and the relationship between Lm/L and the pressure-increasing ability by flow analysis. Table 1 shows the analysis conditions and the results.

In Table 1, C is the clearance in the downstream end of the flight part 7, and D is the inner diameter of the front-end|tip part of the casing 4 (refer FIG. 3). Regarding Conditions 1A to 1C and 2A to 2C, C in Table 1 is C2 in FIG. 3 . In addition, Q is the amount (flow rate) by which material leaks from a clearance part in the direction opposite to an extrusion direction. ΔP is the difference (pressure difference) between the pressure in the casing 4 at the downstream end 11a of the inlet 11 and the pressure in the casing 4 at the tip of the casing 4 . In addition, condition 0 is a reference condition in which the clearance from the upstream side to the downstream end of the casing 4 is always constant at C (= C1 (C1 < C2)). Q0 is the amount (flow rate) of material leaking from the clearance portion under condition 0, and ΔP0 is the pressure difference under condition 0.

Q/Q0 indicates that the higher the value, the higher the dispersion and miscibility of the material. On the other hand, with respect to ?P/?P0, the smaller the value, the higher the boosting capability. When ΔP (pressure difference) is small, the resistance is small. The common analysis condition is that the same amount of material is conveyed, and that the same amount of material is conveyed with a small resistance has a higher pressurization capability. That is, with respect to ?P/?P0, the smaller the value, the higher the boosting capability.

What graphed the analysis result shown in Table 1 is the graph shown in FIG.4 and FIG.5. As can be seen from FIG. 4 , when 0.25 < Lm/L, the dispersion and miscibility of the material increases, and uniform kneading of the material can be promoted. In addition, as can be seen from Fig. 5, by setting Lm/L≤0.4, it is possible to maintain a high voltage boosting capability. Further, from Figs. 4 and 5, when 0.25<Lm/L≤0.4, it is possible to promote uniform kneading of the material while maintaining high pressure-increasing capability.

(Second embodiment)

FIG. 6 is a view corresponding to FIG. 3 showing a second embodiment of the clearance between the top 12 of the flight part 7 and the inner wall surface of the casing 4 .

In the present embodiment, between the downstream end portion 11a of the inlet 11 and the downstream end portion of the flight portion 7, a clearance expanding portion 22 in which the clearance is linearly expanded from the upstream side toward the downstream side is provided. provided (see Fig. 3). With this clearance enlarged portion 22 as a boundary, the clearance on the upstream side of the clearance enlargement portion 22 becomes constant at C1, and the clearance on the downstream side of the clearance enlargement portion 22 becomes constant at C2 (C2>C1). have.

According to this configuration, it is possible to prevent retention of material in the portion where the clearance changes, compared to the case where the portion where the clearance changes is made the above-described clearance step portion 21 .

Also in this embodiment, similarly to the case of the first embodiment shown in FIG. 3 , it is preferable that Lm/L be 0.25<Lm/L, and further preferably 0.25<Lm/L≤0.4. . In addition, Lm is defined as the distance between the downstream end of the flight part 7 and the axial center position of the clearance enlargement part 22 (refer FIG. 6).

(variant example)

FIG. 7 is a view corresponding to FIG. 3 showing a first modification of the clearance between the top 12 of the flight part 7 and the inner wall surface of the casing 4 .

In the embodiment shown in FIG. 6 , the clearance expands linearly from the upstream side toward the downstream side. Instead of this, like the clearance expanding part 23 shown in FIG. 7, it may be a clearance expanding part in which the clearance expands while the clearance change rate becomes small from an upstream to a downstream.

Moreover, like the clearance expansion part 24 shown in FIG. 8, it may become a clearance expansion part in which a clearance expands while a clearance change rate increases from an upstream to a downstream side.

In the above-described embodiments and modifications, there is a region in which the clearance is constant in each of the upstream and downstream portions between the downstream end 11a of the inlet 11 and the downstream end of the flight portion 7 . Between the downstream edge part 11a of the inlet 11 and the downstream edge part of the flight part 7, the area|region with a fixed clearance may exist only in either one of an upstream part and a downstream part.

In the above-described embodiments and modifications, there is a region in which the clearance is constant between the downstream end portion 11a of the inlet 11 and the downstream end portion of the flight portion 7 . In the third modification shown in FIG. 9 , there is no region in which the clearance is constant between the downstream end 11a of the inlet 11 and the downstream end of the flight portion 7, and the downstream end of the inlet 11 ( From 11a) to the downstream end of the flight part 7, the clearance extends linearly from the upstream to the downstream. In addition, from the downstream end 11a of the inlet 11 to the downstream end of the flight part 7, the clearance change rate from the upstream side to the downstream side decreases while the clearance rate increases, and the clearance may be expanded from the upstream side to the downstream side As the clearance change rate increases toward the direction, the clearance may be expanded.

In the above-described embodiment and modification, the clearance between the top 12 and the inner wall surface of the casing 4 is changed by changing the outer diameter of the top 12 of the flight part 7 . Instead of this, the clearance may be changed according to the shape and dimension of the casing 4 .

A pair of right and left screws 2 and 3 of the above-described embodiment are configured to be rotated at the same rotational speed by one driving means. Instead of this, you may be comprised so that a pair of right and left screws 2 and 3 may be rotated independently by two drive means, respectively.

The pressure sensor 5 for measuring the pressure inside the casing 4 (casing downstream portion 14) is not located at the bottom of the casing 4 (casing downstream portion 14), but the casing 4 (casing downstream portion 14). ) may be installed on the side or upper part of the

A screw extruder having only one screw may be used instead of a pair of left and right screws 2 and 3 .

In addition, various changes can be made in the range which a person skilled in the art can imagine.

This application is based on the Japanese patent application (patent application No. 2017-015304) for which it applied on January 31, 2017, The content is taken in here as a reference.

1: Extruder with roller die (screw extruder)
2, 3: screw
4: casing
5: pressure sensor
6: shaft
7: flight part
8, 9: roller
11: Inlet
11a: downstream end
12: top
21: clearance step part
22: clearance enlarged part
C1, C2: clearance

Claims (11)

screw and
A casing that accommodates the screw and is provided with an inlet for material on the upstream side
In a screw extruder for extruding a kneaded product,
The screw has a shaft portion and a spiral flight portion provided on an outer peripheral surface of the shaft portion,
With respect to the clearance between the top portion of the flight portion and the inner wall surface of the casing, the clearance at the downstream end of the flight portion is greater than the clearance at the downstream end of the inlet,
between the downstream end of the inlet and the downstream end of the flight part, characterized in that there is no region in which the clearance is reduced from the upstream side to the downstream side,
Between the downstream end of the inlet and the downstream end of the flight part, there is a clearance step in which the clearance expands stepwise from the upstream side to the downstream side, and the clearances on the upstream and downstream sides of the clearance step are is constant in each,
When the distance between the downstream end of the flight portion and the downstream end of the inlet in the axial direction of the shaft portion is L, and the distance between the downstream end of the flight portion and the clearance step portion is Lm, 0.25 < A screw extruder, characterized in that Lm/L<0.4. delete delete delete screw and
A casing that accommodates the screw and is provided with an inlet for material on the upstream side
In a screw extruder for extruding a kneaded product,
The screw has a shaft portion and a spiral flight portion provided on an outer peripheral surface of the shaft portion,
With respect to the clearance between the top portion of the flight portion and the inner wall surface of the casing, the clearance at the downstream end of the flight portion is greater than the clearance at the downstream end of the inlet,
between the downstream end of the inlet and the downstream end of the flight part, characterized in that there is no region in which the clearance is reduced from the upstream side to the downstream side,
Between the downstream end of the inlet and the downstream end of the flight portion, there is a clearance expanding portion in which the clearance is linearly expanded from the upstream side to the downstream side, and the clearances on the upstream and downstream sides of the clearance expanding portion are respectively is constant in
In the axial direction of the shaft portion, the distance between the downstream end of the flight portion and the downstream end of the inlet is L, and the distance between the downstream end of the flight portion and the axial center position of the clearance expanding portion is Lm. When, a screw extruder, characterized in that 0.25 < Lm / L < 0.4. delete delete delete delete 6. The method of claim 1 or 5,
The screw extruder, characterized in that the clearance is changed according to the outer diameter of the top of the flight part. 6. The method of claim 1 or 5,
a pressure sensor for measuring the pressure inside the casing in a region where the clearance on the downstream side between the downstream end of the inlet and the downstream end of the flight portion is constant;
A screw type extruder characterized in that the rotation speed of the screw is controlled according to the pressure measured by the pressure sensor.

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